Equivalent linear velocity for first arrival picking of seismic refraction

A system, comprising:

• one or more processors;
• and
• a computer-readable storage device coupled to the one or more processors and having instructions stored thereon which, when executed by the one or more processors, cause the one or more processors to perform operations for determining first-arrival onsets for a shot gather for a medium, the operations comprising:
• receiving, by at least one hardware processor, data for the shot gather record, wherein a time for receiving the shot gather is a function of offset for a range of offsets, wherein the range of offsets includes at least two sub-ranges of offsets;
• selecting a particular sub-range of offsets of the range of offsets;
• for each parameter pair of a plurality of parameter pairs, wherein a particular parameter pair is a velocity of sound in the medium and a gradient variable:
• generating a diving wave equation curve for the particular parameter pair;
• and
• integrating, over the particular sub-range of offsets, the shot gather record data corresponding to the diving wave equation curve to generate an equivalent linear velocity value for the particular parameter pair and the shot gather record data;
• selecting, from the equivalent linear velocity values for the plurality of parameter pairs, a greatest equivalent linear velocity value of the equivalent linear velocity values, the greatest equivalent linear velocity value corresponding to a first-arrival parameter pair;
• determining a set of first-arrival onsets for the selected sub-range of offsets from points of the shot gather record data that coincide with a driving wave equation of the first-arrival parameter pair;
• and
• imaging, in near-surface tomography, a subsurface including the medium in a region of interest by seismic data processing of the set of first-arrival onsets.

One or more non-transitory computer-readable storage media coupled to one or more processors and having instructions stored thereon which, when executed by the one or more processors, cause the one or more processors to perform operations for determining first-arrival onsets for a shot gather for a medium, the operations comprising:

• receiving, by at least one hardware processor, data for the shot gather record, wherein a time for receiving the shot gather is a function of offset for a range of offsets, wherein the range of offsets includes at least two sub-ranges of offsets;
• selecting a particular sub-range of offsets of the range of offsets;
• for each parameter pair of a plurality of parameter pairs, wherein a particular parameter pair is a velocity of sound in the medium and a gradient variable:
• generating a diving wave equation curve for the particular parameter pair;
• and
• integrating, over the particular sub-range of offsets, the shot gather record data corresponding to the diving wave equation curve to generate an equivalent linear velocity value for the particular parameter pair and the shot gather record data;
• selecting, from the equivalent linear velocity values for the plurality of parameter pairs, a greatest equivalent linear velocity value of the equivalent linear velocity values, the greatest equivalent linear velocity value corresponding to a first-arrival parameter pair;
• determining a set of first-arrival onsets for the selected sub-range of offsets from points of the shot gather record data that coincide with a driving wave equation of the first-arrival parameter pair;
• and
• imaging, in near-surface tomography, a subsurface including the medium in a region of interest by seismic data processing of the set of first-arrival onsets.